Area-Limited Self-Organized Network Management Method, Communications Apparatus, and System

1. A network management method of an area-limited self-organized wireless network, wherein, only nodes located in a limited area may communicate with each other, the nodes in the self-organized wireless network including a master node or at least one sub node, and there is only one master node in the same limited area, the network management method comprising: a step of, when a communications apparatus which is entering the limited area receives area limiting signals used for indicating a specific area in which network nodes are located, determining by the communications apparatus whether the master node exists in the limited area; a step of, if it is determined that the master node exists, carrying out identity authentication with regard to the master node based on the area limiting signals and letting the communications apparatus be a sub node by the communications apparatus; and a step of, if it is determined that the master node does not exist, letting the communications apparatus be the master node by the communications apparatus, wherein, the master node is in charge of entering of a new sub node and synchronization of shared secret keys between the network nodes, wherein when there are plural master nodes in the network, any one of the plural master nodes sends its priority indicating a priority level of being a master node to other master nodes, and if a master node finds that there is another master node whose priority is higher than that of the master node, then the master node automatically becomes a sub node.

2. The network management method according to claim 1 , wherein: when a new sub node passes through identity authentication with regard to the master node, the master node assigns a shared secret key of a current network to the new sub node, and informs other sub nodes of information related to the new sub node.

3. The network management method according to claim 1 , wherein: the master node detects when a sub node disappears, and in response to the sub node disappearing changes a shared secret key, and informs other sub nodes of the changed shared secret key and a message indicating that the sub node has disappeared.

4. The network management method according to claim 1 , wherein: the master node assigns a priority to each sub node, and the priority indicates a priority level of a corresponding one of the sub nodes becoming a new master node, and when the master node disappears, a sub node having a highest priority automatically becomes a new master node, and informs other sub nodes that the master node has changed.

5. The network management method according to claim 1 , wherein: each sub node automatically detects whether the master node still exists.

6. A communications apparatus comprising: a receiver to receive area limiting signals for limiting an area; a surrounding node detector configured to, when the communications apparatus which is entering the limited area receives the area limiting signals, detect whether there is a master node in the limited area; and a role switch configured to, if it is determined that there is the master node in the limited areas, let the communications apparatus perform identity authentication with regard to the master node based on the area limiting signals so as to become a sub node, and if it is determined that there is not the master node in the limited area, let the communications apparatus be the master node, wherein, the master node is in charge of entering of a new sub node and synchronization of shared secret keys between network nodes of a network, wherein when there are plural master nodes in the network, any one of the plural master nodes sends its priority indicating a priority level of being a master node to other master nodes, and if a master node finds that there is another master node whose priority is higher than that of the master node, then the master node automatically becomes a sub node.

7. The communications apparatus according to claim 6 , wherein: when the communications apparatus becomes the sub node, the communications apparatus has a priority assigned by the master node, and the priority indicates a priority level of the communications apparatus becoming a new master node; and the communications apparatus periodically detects a state of the master node, wherein, if the communications apparatus does not detect existence of the master node in a predetermined time period, and the priority of the communications apparatus is a highest one compared to those of other sub nodes, then the communications apparatus automatically becomes a new master node, and informs the other sub nodes that the master node has changed.

8. The communications apparatus according to claim 6 , wherein: when the communications apparatus becomes the master node, the communications apparatus periodically detects states of the respective sub nodes, wherein, if the communications apparatus does not detect existence of a sub node in a predetermined time period, then the communications apparatus regards the sub node as having disappeared, changes a shared secret key, informs other sub nodes of the changed shared secret key, and sends a message indicating that the sub node has disappeared.

9. An area-limited wireless communications system comprising: area limiting signal transmitting apparatuses configured to transmit area limiting signals for limiting an area; and plural wireless communications apparatuses dynamically located in the limited area, wherein: one of the plural wireless communications apparatuses serves as a master node, and the others serve as sub nodes, wherein, the master node is in charge of entering of a new sub node and synchronization of shared secret keys between network nodes of a network, and when the master node disappears, one of the sub nodes automatically becomes a new master node, in a case where there is only one wireless communications apparatus in the area-limited wireless communications system, the wireless communications apparatus becomes the master node; after that, when a new wireless communications apparatus enters, the new wireless communications apparatus becomes a sub node, each sub node has a priority assigned by the master node, and the priority indicates a priority level of a corresponding one of the sub nodes becoming a new master node; one of the communications apparatuses serving as a sub node periodically detects a state of the master node, wherein, if said one of the sub nodes does not detect the master node in a predetermined time period, and the priority of said one of the sub nodes is higher than those of other sub nodes, then said one of the sub nodes automatically becomes a new master node, and informs the other sub nodes that the master node has changed, the master node periodically detects states of the respective sub nodes, wherein, if the master node does not detect a sub node in a predetermined time period, then the master node regards the non-detected sub node as having disappeared, changes a shared secret key, and informs other sub nodes of the changed shared secret keys and information indicating that the non-detected sub node has disappeared, and when there are plural master nodes in the network, any one of the plural master nodes sends its priority indicating a priority level of being a master node to other master nodes, and if a master node finds that there is another master node whose priority is higher than that of the master node, then the master node automatically becomes a sub node.